Acceleration enrichment

ABSTRACT

In a speed-density fuel injection system, a pressure transducer receives pressure signals from the air induction passage below the throttle and from a port located closely above and traversed by the throttle. The atmospheric pressure sensed by the port during closed throttle operation increases the induction passage pressure signal otherwise delivered to the transducer. As the throttle is opened, increased fuel flow is provided for acceleration enrichment until the increased pressure signal reduces to induction passage pressure.

United States Patent 1191 Sciabica July 23, 1974 ACCELERATION ENRICHMENT 2,922,630 1/1960 Stoltman 123/140 MP 3,566,847 3/1971 Scholl et al 123/140 MC [75] lnvemor' Franc 3,726,261 4/1973 Sauer 123/32 EA [73] Assignee: General Motors Corporation,

Detroit, Mich, Primary Examiner-Laurence M. Goodridge Filed Mar 31 1972 Attorney, Agent, or FirmC. K. Veenstra [21] Appl. No.: 240,184 [57] ABSTRACT In a speed-density fuel injection system, a pressure 52 mg C| 123 32 EA, 123/119 R 123/139 w transducer receives pressure signals from the air in- 123/140 MC duction passage below the throttle and from a port 10- 51 Int. Cl. F02d 5/02 eeied eleeely above and traversed by the throttle The 58 Field of Search 123/140 MP, 32 EA atmospheric Pressure sensed y the P during closed throttle operation increases the induction passage 5 References Cited pressure signal otherwise delivered to the transducer. UNITED STATES PATENTS As the throttle is opened, increased fuel flow is provided for acceleration enrichment until the increased 3 321 /432: i igzii i c 123/140 MP pressure signal reduces to induction passage pressure. 2,894,735 7/1959 Zupancic 123/140 MP 1 Claim, 1 Drawing Figure IIZ'I IIIIIIIIIIIIIIIIII/ 1 ACCELERATION ENRICHMENT This invention relates to speed-density responsive fuel systems for internal combustion engines and more particularly to a density or pressure signal passage construction which provides an increased pressure signal for acceleration enrichment as the throttle is opened to accelerate from idling speed.

In known speed-density fuel injection systems, a fuel injector nozzle is energized each cycle of the engine for a period determined by the density or pressure of the air in the induction passage as sensed by a pressure transducer. Increases in induction passage pressure are indicative of increases in air flow to the engine, and the duration of fuel flow from the injector is accordingly increased.

However, these systems often do not provide sufficient fuel flow as the throttle is opened to accelerate the engine from idling speed. Various enrichment mechanisms have been proposed to increase fuel flow at this time, such as the valve mechanism shown in U.S. Pat. No. 3,566,847. r

This invention provides a means for increasing fuel flow as the engine accelerates from idling speed which obviates the need for such complex valve mechanisms. As provided by this invention, the induction passage pressure signal sensedby the transducer during open throttle operation is increased by an atmospheric bleed from just above the throttle during closed throttle operation. When the throttle is opened, a certain period of time is required to reduce the increased pressure signal sensed by the transducer, and fuel flow is increased during this period.

The details as well as other objects and advantages of this invention are set forth below.

The drawing illustrates the fuel injection system and comprises a schematic of the electronic control circuit and intake manifold associated with said system.

Referring to the drawing, the induction passage has a throttle 12 which is rotatable between the closed position shown and open positions to control air flow to the engine. An injector nozzle 14 is disposed to discharge-into induction passage 10 adjacent the inlet valve 16 for the engine combustion chamber. A separate nozzle 14 would ordinarily be provided for each combustion chamber.

The electronic control circuit includes a unit 18 which applies a negative pulse to line 20 each time solenoid operated nozzle 14 is to be energized that is, each time fuel must be supplied for combustion in the associated combustion chamber. The negative pulse renders an output transistor 22 nonconductive. With output transistor 22 off, current flows through a sole- I noid winding 24 to energize nozzle 14 and initiate fuel injection. Nozzle 14 remains energized for a period of time determined by the remainder of the electronic control circuit.

The negative pulse also renders a control transistor 26 nonconductive. With control transistor 26 off, the voltage at a junction 28 increases and renders a transistor 30 conductive which in turn renders a transistor 32 nonconductive. With trnsistor 32 off, transistors 34 and 36 also are renderednonconductive. As long as transistor 36 is off, output transistor 22 remains off and permits current flow through solenoid 24 to energize injection nozzle 14.

The aforementioned transistors are maintained in the indicated state for a period of time determined by the L/R time constant provided by the inductance of the coil 38 and the combined resistances of the resistors 40 and 44. When the time constant permits decay of the voltage at junction 28 to a predetennined level, transistor 30 is rendered nonconductive and transistor 32 is thereby rendered conductive. With transistor 32 on, transistors 34 and 36 are rendered conductive. As transistor 36 becomes conductive, output transistor 22 becomes conductive, preventing current flow through solenoid 24 to de-energize nozzle 14 and terminate fuel injection.

Thus the duration of fuel injection is controlled by the level of a voltage signal at junction 28 which in turn is controlled by an L/R time constant. In the simplified electronic control circuit shown here for purposes of illustration, this time constant is varied primarily by varying the inductance of coil 38.

The inductance of coil 38 varies with the position of a plunger 46 which is controlled by a pressure transducer 48 in response to pressure signals received from induction passage 10. The construction of transducer 48, plunger 46 and coil 38 may be as depicted in US. Pat. application Ser. No. 202,760 filed Nov. 29, 1971.

Transducer 48 is connected to induction passage 10 downstream of throttle 12 by a signal passage 50. Upon an increase in the absolute pressure in induction passage 10, indicative of an increase in combustion air flow through induction passage 10, transducer 48 moves plunger 46 to increase the inductance of coil 38 and thereby increases the duration of fuel injection. Conversely, as the induction passage pressure decreases with decreasing air flow, the inductance is decreased to decrease the duration of fuel injection.

Transducer 48 also is connected to induction passage 10 by another signal passage 52 which opens into induction passage 10 at a port 54 located upstream of throttle 12 when throttle 12 is closed as shown and located downstream of throttle 12 when throttle 12 is open. During closed throttle, idling operation, signal passage 52 bleeds air at substantially atmospheric pressure into transducer 48 to provide an effective increase in the induction passage pressure otherwise sensed through signal passage 50. This increase in pressure causes an increase in the inductance of coil 38 to increase the duration of fuel injection.

As throttle 12 is opened from the closed position shown, the pressure at port 54 changes from substantially atmospheric to the lower induction pressure downstream of throttle 12. A certain period of time will be required to reduce the effective pressure sensed by transducer 48 from the increased pressure provided by a combination of atmospheric and induction pressure to the lower induction pressure alone. During this period, transducer 38 acts through plunger 46 and coil 38 to provide an increased duration of fuel injection, thereby increasing the fuel flow to provide an enriched mixture. Thus with this construction, no separate mechanism is required to provide acceleration enrichment.

During open throttle operation, signal passages 50 and 52 deliver the same pressure to transducer 48. Thus during steady state open throttle operation, signal passage 52 and port 54 have no effect on the system.

It will be appreciated that the duration of acceleration enrichment provided by this construction may be controlled by appropriate restrictions in passages 50 and 52 and by appropriate selection of the volume in passages 50 and 52 and in transducer 48.

It also, will be recognized that incorporation of signal passage 52 provides an increase in the effective pressure sensed by transducer 48 during closed throttle, engine idling conditions. If this increased pressure causes too great an increase in idle fuel flow from injector 14, a switch 56 may be connected to and opened by throttle l2 whenever throttle 12 is closed. Opening of switch 56 adds a resistor 58 to the circuit and reduces the L/R time constant to reduce idle fuel flow.

Therefore, as the throttle is moved from closed position to open position, port 54 is covered and switch 56 is opened. The effective pressure sensed by transducer 48 remains temporarily elevated above induction pressure. With the increased L/R time constant available due to opening of switch 56, the temporarily elevated pressure causes increased fuel flow for acceleration enrichment. This enrichment decays as the elevated pressure signal is reduced by the action of induction pressure on passages 50 and 52 so that off-idle fuel flow is reduced for cruise operation.

It should be made apparent that switch 56 is closed whenever port 54 is above throttle l2 and open whenever port 54 is below throttle 12. Thus, no excess offidle enrichment will occur. Of course, the relative tim- 4 passage and rotatable between open and closed positions for controlling said air flow, a transducer for sensing the pressure existing in the induction passage, a fuel injector adjoining said induction passage and energized to supply fuel thereto each cycle of the engine for a period determined by said transducer, a first signal passage extending to said transducer from said induction passage downstream of said throttle for communicating an induction passage pressure signal to said transducer, whereby said transducer may control fuel delivery to the engine in accordance with the absolute pressure in said induction passage downstream of said throttle, a second signal passage forming a bleed opening extending to said transducer from a location in said induction passage upstream of said throttle when said throttle is in said closed position and downstream of said throttle when said throttle is in said open position, whereby the pressure sensed by said transducer is higher when said throttle is in said closed position and as said throttle is opened from said closed position than when said throttle is in said open position, and means responsive to throttle position for reducing said period for energizing said injector when said throttle is in said closed posiing of the operation of switch 56 and the exposure of port 54 may be varied to achieve richer or leaner mixtures in relation to throttle position, but this is not necessary for the proper operation of this invention.

I claim:

1. For use in an internal combustion engine, a speeddensity responsive fuel injection system comprising an induction passage for air flow to the combustion chamber of said engine, a throttle disposed in said induction tion, said transducer thereby causing a substantially increased period of fuel delivery to said induction passage for combustion in said engine during opening movement of said throttle from said closed position as would occur during acceleration than would be provided were said transducer responsive solely to the absolute pressure in said induction passage downstream of said throttle, and said maans for reducing said period for energizing said injector when said throttle is in said closed position thereby counteracting the tendency of said transducer to increase fuel delivery when said throttle is in said closed position as would be desirable when said engine is idling. 

1. For use in an internal combustion engine, a speed-density responsive fuel injection system comprising an induction passage for air flow to the combustion chamber of said engine, a throttle disposed in said induction passage and rotatable between open and closed positions for controlling said air flow, a transducer for sensing the pressure existing in the induction passage, a fuel injector adjoining said induction passage and energized to supply fuel thereto each cycle of the engine for a period determined by said transducer, a first signal passage extending to said transducer from said induction passage downstream of said throttle for communicating an induction passage pressure signal to said transducer, whereby said transducer may control fuel delivery to the engine in accordance with the absolute pressure in said induction passage downstream of said throttle, a second signal passage forming a bleed opening extending to said transducer from a location in said induction passage upstream of said throttle when said throttle is in said closed position and downstream of said throttle when said throttle is in said open position, whereby the pressure sensed by said transducer is higher when said throttle is in said closed position and as said throttle is opened from said closed position than when said throttle is in said open position, and means responsive to throttle position for reducing said period for energizing said injector when said throttle is in said closed position, said transducer thereby causing a substantially increased period of fuel delivery to said induction passage for combustion in said engine during opening movement of said throttle from said closed position as would occur during acceleration than would be provided were said transducer responsive solely to the absolute pressure in said induction passage downstream of said throttle, and said maans for reducing said period for energizing said injector when said throttle is in said closed position thereby counteracting the tendency of said transducer to increase fuel delivery when said throttle is in said closed position as would be desirable when said engine is idling. 